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High Power MicroSpot Focusing Objectives


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Features

  • Designed for High-Power Industrial Nd:YAG Lasers
  • Magnifications: 5X, 10X, or 20X
  • Design Wavelengths: 532 nm or 1064 nm

Specifications

  • Fused Silica Lenses
  • Better than 96 to 98% Transmission within Design Spectral Region
  • Damage Threshold of 500 MW/cm2 for 20 ns Pulses @ 20 Hz (532 or 1064 nm)

Thorlabs' High-Power Nd:YAG MicroSpot Focusing Objectives are designed to focus high-power Nd:YAG laser beams to a diffraction-limited spot. They offer a damage threshold of 500 MW/cm2 at 532 nm or 1064 nm (20 ns, 20 Hz pulses).

This objective is capable of producing a near-diffraction-limited spot size when used with a monochromatic source within the 250 - 1600 nm range. However, if used at a wavelength other than the design wavelength, the effective focal length listed on the Specs tab will shift and the AR coating will no longer be optimized; see the Specs tab for AR coating plots. Custom AR Coatings are available to optimize the performance of these objectives at other wavelengths.

High Power MicroSpot Focusing Objectives

Item #λcMWDEFLNAEADamage Threshold
LMH-5X-532 532 nm 5X 35 mm 40 mm 0.13 10 mm 10 J/cm2 (532 nm, 20 Hz, 10 ns, Ø200 µm)
LMH-10X-532 10X 15 mm 20 mm 0.25 10 mm
LMH-20X-532 20X 6 mm 10 mm 0.40 8 mm
LMH-5X-1064 1064 nm 5X 35 mm 40 mm 0.13 10 mm 20 J/cm2 (1064 nm, 20 Hz, 10 ns, Ø400 µm)
LMH-10X-1064 10X 15 mm 20 mm 0.25 10 mm
LMH-20X-1064 20X 6 mm 10 mm 0.40 8 mm

λc = Center Wavelength, M = Magnification, WD = Working Distance

EFL = Effective Focal Length, NA = Numerical Aperture, EA = Entrance Aperture

Damage Threshold Specifications
Item # Suffix Damage Threshold
-532 10 J/cm2 (532 nm, 20 Hz, 10 ns, Ø200 µm)
-1064 20 J/cm2 (1064 nm, 20 Hz, 10 ns, Ø400 µm)

Damage Threshold Data for High Power Focusing Objectives AR Coatings

The specifications to the right are measured data for the antireflective (AR) coatings deposited onto the optical surface of our high power focusing objectives. Damage threshold specifications are constant for a given coating type, regardless of the focal length.

 

Laser Induced Damage Threshold Tutorial

This following is a general overview of how laser induced damage thresholds are measured and how the values may be utilized in determining the appropriateness of an optic for a given application. When choosing optics, it is important to understand the Laser Induced Damage Threshold (LIDT) of the optics being used. The LIDT for an optic greatly depends on the type of laser you are using. Continuous wave (CW) lasers typically cause damage from thermal effects (absorption either in the coating or in the substrate). Pulsed lasers, on the other hand, often strip electrons from the lattice structure of an optic before causing thermal damage. Note that the guideline presented here assumes room temperature operation and optics in new condition (i.e., within scratch-dig spec, surface free of contamination, etc.). Because dust or other particles on the surface of an optic can cause damage at lower thresholds, we recommend keeping surfaces clean and free of debris. For more information on cleaning optics, please see our Optics Cleaning tutorial.

Testing Method

Thorlabs' LIDT testing is done in compliance with ISO/DIS11254 specifications. A standard 1-on-1 testing regime is performed to test the damage threshold.

First, a low-power/energy beam is directed to the optic under test. The optic is exposed in 10 locations to this laser beam for a set duration of time (CW) or number of pulses (prf specified). After exposure, the optic is examined by a microscope (~100X magnification) for any visible damage. The number of locations that are damaged at a particular power/energy level is recorded. Next, the power/energy is either increased or decreased and the optic is exposed at 10 new locations. This process is repeated until damage is observed. The damage threshold is then assigned to be the highest power/energy that the optic can withstand without causing damage. A histogram such as that below represents the testing of one BB1-E02 mirror.

LIDT metallic mirror
The photograph above is a protected aluminum-coated mirror after LIDT testing. In this particular test, it handled 0.43 J/cm2 (1064 nm, 10 ns pulse, 10 Hz, Ø1.000 mm) before damage.
LIDT BB1-E02
Example Test Data
Fluence# of Tested LocationsLocations with DamageLocations Without Damage
1.50 J/cm2 10 0 10
1.75 J/cm2 10 0 10
2.00 J/cm2 10 0 10
2.25 J/cm2 10 1 9
3.00 J/cm2 10 1 9
5.00 J/cm2 10 9 1

According to the test, the damage threshold of the mirror was 2.00 J/cm2 (532 nm, 10 ns pulse, 10 Hz, Ø0.803 mm). Please keep in mind that it is only representative of one coating run and that Thorlabs' specified damage thresholds account for coating variances.

Continuous Wave and Long-Pulse Lasers

When an optic is damaged by a continuous wave (CW) laser, it is usually due to the melting of the surface as a result of absorbing the laser's energy or damage to the optical coating (antireflection) [1]. Pulsed lasers with pulse lengths longer than 1 µs can be treated as CW lasers for LIDT discussions. Additionally, when pulse lengths are between 1 ns and 1 µs, LIDT can occur either because of absorption or a dielectric breakdown (must check both CW and pulsed LIDT). Absorption is either due to an intrinsic property of the optic or due to surface irregularities; thus LIDT values are only valid for optics meeting or exceeding the surface quality specifications given by a manufacturer. While many optics can handle high power CW lasers, cemented (e.g., achromatic doublets) or highly absorptive (e.g., ND filters) optics tend to have lower CW damage thresholds. These lower thresholds are due to absorption or scattering in the cement or metal coating.

Linear Power Density Scaling

LIDT in linear power density vs. pulse length and spot size. For long pulses to CW, linear power density becomes a constant with spot size. This graph was obtained from [1].

Intensity Distribution

Pulsed lasers with high pulse repetition frequencies (PRF) may behave similarly to CW beams. Unfortunately, this is highly dependent on factors such as absorption and thermal diffusivity, so there is no reliable method for determining when a high PRF laser will damage an optic due to thermal effects. For beams with a large PRF both the average and peak powers must be compared to the equivalent CW power. Additionally, for highly transparent materials, there is little to no drop in the LIDT with increasing PRF.

In order to use the specified CW damage threshold of an optic, it is necessary to know the following:

  1. Wavelength of your laser
  2. Linear power density of your beam (total power divided by 1/e2 spot size)
  3. Beam diameter of your beam (1/e2)
  4. Approximate intensity profile of your beam (e.g., Gaussian)

The power density of your beam should be calculated in terms of W/cm. The graph to the right shows why the linear power density provides the best metric for long pulse and CW sources. Under these conditions, linear power density scales independently of spot size; one does not need to compute an adjusted LIDT to adjust for changes in spot size. This calculation assumes a uniform beam intensity profile. You must now consider hotspots in the beam or other nonuniform intensity profiles and roughly calculate a maximum power density. For reference, a Gaussian beam typically has a maximum power density that is twice that of the uniform beam (see lower right).

Now compare the maximum power density to that which is specified as the LIDT for the optic. If the optic was tested at a wavelength other than your operating wavelength, the damage threshold must be scaled appropriately. A good rule of thumb is that the damage threshold has a linear relationship with wavelength such that as you move to shorter wavelengths, the damage threshold decreases (i.e., a LIDT of 10 W/cm at 1310 nm scales to 5 W/cm at 655 nm). While this rule of thumb provides a general trend, it is not a quantitative analysis of LIDT vs wavelength. In CW applications, for instance, damage scales more strongly with absorption in the coating and substrate, which does not necessarily scale well with wavelength. While the above procedure provides a good rule of thumb for LIDT values, please contact Tech Support if your wavelength is different from the specified LIDT wavelength. If your power density is less than the adjusted LIDT of the optic, then the optic should work for your application.

Please note that we have a buffer built in between the specified damage thresholds online and the tests which we have done, which accommodates variation between batches. Upon request, we can provide individual test information and a testing certificate. The damage analysis will be carried out on a similar optic (customer's optic will not be damaged). Testing may result in additional costs or lead times. Contact Tech Support for more information.

Pulsed Lasers

As previously stated, pulsed lasers typically induce a different type of damage to the optic than CW lasers. Pulsed lasers often do not heat the optic enough to damage it; instead, pulsed lasers produce strong electric fields capable of inducing dielectric breakdown in the material. Unfortunately, it can be very difficult to compare the LIDT specification of an optic to your laser. There are multiple regimes in which a pulsed laser can damage an optic and this is based on the laser's pulse length. The highlighted columns in the table below outline the pulse lengths that our specified LIDT values are relevant for.

Pulses shorter than 10-9 s cannot be compared to our specified LIDT values with much reliability. In this ultra-short-pulse regime various mechanics, such as multiphoton-avalanche ionization, take over as the predominate damage mechanism [2]. In contrast, pulses between 10-7 s and 10-4 s may cause damage to an optic either because of dielectric breakdown or thermal effects. This means that both CW and pulsed damage thresholds must be compared to the laser beam to determine whether the optic is suitable for your application.

Pulse Duration t < 10-9 s 10-9 < t < 10-7 s 10-7 < t < 10-4 s t > 10-4 s
Damage Mechanism Avalanche Ionization Dielectric Breakdown Dielectric Breakdown or Thermal Thermal
Relevant Damage Specification N/A Pulsed Pulsed and CW CW

When comparing an LIDT specified for a pulsed laser to your laser, it is essential to know the following:

Energy Density Scaling

LIDT in energy density vs. pulse length and spot size. For short pulses, energy density becomes a constant with spot size. This graph was obtained from [1].

  1. Wavelength of your laser
  2. Energy density of your beam (total energy divided by 1/e2 area)
  3. Pulse length of your laser
  4. Pulse repetition frequency (prf) of your laser
  5. Beam diameter of your laser (1/e2 )
  6. Approximate intensity profile of your beam (e.g., Gaussian)

The energy density of your beam should be calculated in terms of J/cm2. The graph to the right shows why the energy density provides the best metric for short pulse sources. Under these conditions, energy density scales independently of spot size, one does not need to compute an adjusted LIDT to adjust for changes in spot size. This calculation assumes a uniform beam intensity profile. You must now adjust this energy density to account for hotspots or other nonuniform intensity profiles and roughly calculate a maximum energy density. For reference a Gaussian beam typically has a maximum power density that is twice that of the 1/e2 beam.

Now compare the maximum energy density to that which is specified as the LIDT for the optic. If the optic was tested at a wavelength other than your operating wavelength, the damage threshold must be scaled appropriately [3]. A good rule of thumb is that the damage threshold has an inverse square root relationship with wavelength such that as you move to shorter wavelengths, the damage threshold decreases (i.e., a LIDT of 1 J/cm2 at 1064 nm scales to 0.7 J/cm2 at 532 nm):

Pulse Wavelength Scaling

You now have a wavelength-adjusted energy density, which you will use in the following step.

Beam diameter is also important to know when comparing damage thresholds. While the LIDT, when expressed in units of J/cm2, scales independently of spot size; large beam sizes are more likely to illuminate a larger number of defects which can lead to greater variances in the LIDT [4]. For data presented here, a <1 mm beam size was used to measure the LIDT. For beams sizes greater than 5 mm, the LIDT (J/cm2) will not scale independently of beam diameter due to the larger size beam exposing more defects.

The pulse length must now be compensated for. The longer the pulse duration, the more energy the optic can handle. For pulse widths between 1 - 100 ns, an approximation is as follows:

Pulse Length Scaling

Use this formula to calculate the Adjusted LIDT for an optic based on your pulse length. If your maximum energy density is less than this adjusted LIDT maximum energy density, then the optic should be suitable for your application. Keep in mind that this calculation is only used for pulses between 10-9 s and 10-7 s. For pulses between 10-7 s and 10-4 s, the CW LIDT must also be checked before deeming the optic appropriate for your application.

Please note that we have a buffer built in between the specified damage thresholds online and the tests which we have done, which accommodates variation between batches. Upon request, we can provide individual test information and a testing certificate. Contact Tech Support for more information.


[1] R. M. Wood, Optics and Laser Tech. 29, 517 (1997).
[2] Roger M. Wood, Laser-Induced Damage of Optical Materials (Institute of Physics Publishing, Philadelphia, PA, 2003).
[3] C. W. Carr et al., Phys. Rev. Lett. 91, 127402 (2003).
[4] N. Bloembergen, Appl. Opt. 12, 661 (1973).

Click the Support Documentation icon document icon or Part Number below to view the available support documentation
Part NumberProduct Description
LMH-10X-1064 Support Documentation LMH-10X-1064:1064 nm, 10X High-Power MicroSpot Focusing Objective
LMH-10X-532 Support Documentation LMH-10X-532:532 nm, 10X High-Power MicroSpot Focusing Objective
LMH-20X-1064 Support Documentation LMH-20X-1064:1064 nm, 20X High-Power MicroSpot Focusing Objective
Part NumberProduct Description
LMH-20X-532 Support Documentation LMH-20X-532:532 nm, 20X High-Power MicroSpot Focusing Objective
LMH-5X-1064 Support Documentation LMH-5X-1064:1064 nm, 5X High-Power MicroSpot Focusing Objective
LMH-5X-532 Support Documentation LMH-5X-532:532 nm, 5X High-Power MicroSpot Focusing Objective

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Posted Comments:
Poster:suwas.nikumb
Posted Date:2014-02-10 09:37:53.92
Do you have microscope objectives at 532nm and 800nm with atleast 12-15mm entrance aperture?
Poster:besembeson
Posted Date:2014-02-12 01:59:58.0
Response from Bweh E. at Thorlabs: Thanks for contacting Thorlabs. At this time, we do not carry such objectives that meet your requirements. We however have several other objectives at the following page: http://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=1044.
Poster:jlow
Posted Date:2013-09-19 14:09:00.0
Response from Jeremy at Thorlabs: We do not currently have these short focal length objectives for high power application. I have logged this in our internal forum and we will look into whether we could make this.
Poster:lvtaohn
Posted Date:2013-09-17 19:08:25.967
Do you have 40times or 60 times high power focusing objective 1064nm or 532nm? I need them in these days. Please let me know if you have them. Thank you!
Poster:rpscott
Posted Date:2013-05-29 17:06:42.537
Is the transmission for the 1064nm version of the objectives similar at 1037nm?
Poster:tcohen
Posted Date:2013-05-30 02:28:00.0
Response from Tim at Thorlabs: Yes. The number of surfaces in each objective is different and therefore deviation away from the design wavelength will have more of an impact on transmission for the 20X vs the 10X, for example. However, at your desired wavelength the total transmission for each is similar.
Poster:tcohen
Posted Date:2012-08-23 16:25:00.0
Response from Tim at Thorlabs: Thank you for contacting us. I’ve emailed you to go over this objective and supply some representative data.
Poster:song31037
Posted Date:2012-08-23 15:19:04.0
Can I receive the wavelength range information of LMH-20X-1064?
Poster:tcohen
Posted Date:2012-02-29 15:56:00.0
Response from Tim at Thorlabs: Thank you for your feedback on the LMH-10X-532. I am looking into the materials we use for this objective and will post an update soon.
Poster:g.laliberte
Posted Date:2012-02-29 10:13:58.0
I'm intersted in a microscope objective that would be made of non magnetic material. Do you have any data about the housing material of that lens? THanks
Poster:jjurado
Posted Date:2011-07-08 08:58:00.0
Response from Javier at Thorlabs to last poster: Thank you very much for contacting us. For this objective, the absorption in the glass itself is almost negligible, and if we assume 3.5% loss at each surface we would end up with a total transmission in the neighborhood of 80%. However, keep in mind that the chromatic shift of roughly 0.2 mm will slightly affect the performance of this objective. Also, we do not currently have an objective specifically designed for operation at 980 and 1550 nm. Please contact us at techsupport@thorlabs.com if you would like to discuss your application a bit further.
Poster:
Posted Date:2011-07-07 14:17:40.0
I am working with this objective (LMH-10X-1064), but I have beam at 1550nm. So I want to know the transmission spectrum of this objective especialy for 1550nm). Is there any particular objective design to work at 980nm and 1550nm?
Poster:apalmentieri
Posted Date:2009-12-31 17:12:33.0
A response from Adam at Thorlabs to Ilday: There was a server glitch and we are working to bring this page online. Please note that we do have stock on most of these objectives and they can be ordered direct through our sales department, sales@thorlabs.com or 973-300-3000, while these parts are not on the website. I will email you with more information.
Poster:ilday
Posted Date:2009-12-31 17:01:39.0
I wanted to purchase this product, which was available until yesterday, however it has disappeared from the webpage. Is that a server glitch or did you discontinue the product?
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Microscope Objective Camera Lens Mounts  rms  

532 nm High Power MicroSpot Focusing Objectives

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal/Imperial Price Available / Ships
LMH-5X-532 Support Documentation
LMH-5X-532532 nm, 5X High-Power MicroSpot Focusing Objective
$822.00
Today
LMH-10X-532 Support Documentation
LMH-10X-532532 nm, 10X High-Power MicroSpot Focusing Objective
$1,010.00
Today
LMH-20X-532 Support Documentation
LMH-20X-532532 nm, 20X High-Power MicroSpot Focusing Objective
$1,500.00
3-5 Days

1064 nm High Power MicroSpot Focusing Objectives

Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal/Imperial Price Available / Ships
LMH-5X-1064 Support Documentation
LMH-5X-10641064 nm, 5X High-Power MicroSpot Focusing Objective
$822.00
Today
LMH-10X-1064 Support Documentation
LMH-10X-10641064 nm, 10X High-Power MicroSpot Focusing Objective
$1,010.00
Today
LMH-20X-1064 Support Documentation
LMH-20X-10641064 nm, 20X High-Power MicroSpot Focusing Objective
$1,500.00
Today
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